The present invention broadly relates to a seal between opposing flat surfaces of two members which make a relative movement to each other and, more particularly, to a multiple annular seal ring composed of a plurality of concentrically tiered seal elements, said seal ring having a tapered surface and adapted to be received in an annular groove having a tapered bottom surface formed in either one of these members, as well as to a sealing device incorporating the multiple annular seal ring.
Generally speaking, the seal between the inner peripheral surface of cylinder and the outer peripheral surface of the piston of internal combustion engine is performed by annular seal rings called piston rings which are cut at their intermediate portions. These piston rings, thanks to the provision of the cut portions, exhibit radial expanding force. This radial expanding force acts to press the outer peripheral surface of the piston ring against the inner peripheral surface of the cylinder so as to enable the piston ring to form a good seal between the inner peripheral surface of the cylinder and the outer peripheral surface of the piston.
This advantage of the conventional piston ring i.e. the radial expansion of the ring however, cannot be utilized in the seal between the inner side surface of the housing and the side surface of the rotor of rotary-piston type internal combustion engine.
It has been a conventional measure, therefore, for obtaining the required sealing force between the side surfaces of the rotor and housing, to press a seal ring which itself has no expanding force, against the sealing surface, by means of springs or the like resilient means disposed behind the seal ring.
More specifically, as will be seen from FIG. 1 showing a typical example of conventional sealing arrangement, a seal ring 1 adapted to make a seal between the side surface R of the rotor and the side surface H of the housing is resiliently pressed by springs 2 against the surface H of the housing. In order to ensure a sufficient sealing effect at the sealing faces of the seal ring 1, gaps h and h' are left between the radially inner and outer surfaces, and the opposing walls of the annular groove G for receiving the seal ring 1. As a result, lubricating oil is allowed to leak from the radially inner portion of the rotor to the peripheral portion of the rotor, through these gaps and the clearance behind the seal ring 1 where the springs 2 are disposed.
Various counter-measures have been taken to avoid such a leakage of lubricating oil. For instance, it has been proposed to form a groove 3 in the seal ring 1 itself, so as to receive an "O" ring 4 adapted to make a seal between the rotor and the seal ring itself, as shown in FIG. 1. It has been also practiced to use an oil seal 6, in place of the "O" ring 4, as shown in FIG. 2.
These conventional sealing arrangement, however, have following disadvantages. Namely, the seal ring 1 which operates under severe condition of high temperature and pressure, is always made to move in the groove G toward one side of the groove G, as the rotor makes a complicated eccentric rotary movement. As a result, the above mentioned gaps h and h' are made to change, to nullify the above-explained sealing effect. Therefore, the seal ring 1 fails to perform the sealing function to allow the lubricating oil around the crank shaft, gears and the like at the center of the rotor to leak into the combustion chamber partly defined by the outer peripheral surface of the rotor, through the gaps h, h' and the clearance behind the seal ring 1.
Further, the combustion gas of a high pressure is allowed to leak from the combustion chamber to the low-pressure side, through these gaps and clearance.
These leaks of lubricating oil and combustion gas inconveniently lower the performance of the rotary-piston type internal combustion engine and, further, poses various problems such as deterioration of combustion resulting in uneconomically large rate of fuel consumption and increased emission of noxious components to the atmosphere.